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469 lines
11 KiB
469 lines
11 KiB
/* |
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* LibXDiff by Davide Libenzi ( File Differential Library ) |
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* Copyright (C) 2003 Davide Libenzi |
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* |
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* This library is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* This library is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with this library; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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* |
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* Davide Libenzi <davidel@xmailserver.org> |
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* |
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*/ |
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#include "xinclude.h" |
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#define XDL_MAX_COST_MIN 256 |
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#define XDL_HEUR_MIN_COST 256 |
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#define XDL_LINE_MAX (long)((1UL << (8 * sizeof(long) - 1)) - 1) |
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#define XDL_SNAKE_CNT 20 |
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#define XDL_K_HEUR 4 |
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typedef struct s_xdpsplit { |
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long i1, i2; |
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int min_lo, min_hi; |
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} xdpsplit_t; |
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static long xdl_split(unsigned long const *ha1, long off1, long lim1, |
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unsigned long const *ha2, long off2, long lim2, |
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long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl, |
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xdalgoenv_t *xenv); |
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static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2); |
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/* |
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* See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers. |
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* Basically considers a "box" (off1, off2, lim1, lim2) and scan from both |
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* the forward diagonal starting from (off1, off2) and the backward diagonal |
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* starting from (lim1, lim2). If the K values on the same diagonal crosses |
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* returns the furthest point of reach. We might end up having to expensive |
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* cases using this algorithm is full, so a little bit of heuristic is needed |
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* to cut the search and to return a suboptimal point. |
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*/ |
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static long xdl_split(unsigned long const *ha1, long off1, long lim1, |
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unsigned long const *ha2, long off2, long lim2, |
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long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl, |
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xdalgoenv_t *xenv) { |
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long dmin = off1 - lim2, dmax = lim1 - off2; |
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long fmid = off1 - off2, bmid = lim1 - lim2; |
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long odd = (fmid - bmid) & 1; |
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long fmin = fmid, fmax = fmid; |
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long bmin = bmid, bmax = bmid; |
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long ec, d, i1, i2, prev1, best, dd, v, k; |
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/* |
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* Set initial diagonal values for both forward and backward path. |
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*/ |
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kvdf[fmid] = off1; |
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kvdb[bmid] = lim1; |
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for (ec = 1;; ec++) { |
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int got_snake = 0; |
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/* |
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* We need to extent the diagonal "domain" by one. If the next |
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* values exits the box boundaries we need to change it in the |
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* opposite direction because (max - min) must be a power of two. |
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* Also we initialize the extenal K value to -1 so that we can |
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* avoid extra conditions check inside the core loop. |
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*/ |
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if (fmin > dmin) |
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kvdf[--fmin - 1] = -1; |
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else |
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++fmin; |
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if (fmax < dmax) |
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kvdf[++fmax + 1] = -1; |
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else |
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--fmax; |
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for (d = fmax; d >= fmin; d -= 2) { |
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if (kvdf[d - 1] >= kvdf[d + 1]) |
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i1 = kvdf[d - 1] + 1; |
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else |
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i1 = kvdf[d + 1]; |
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prev1 = i1; |
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i2 = i1 - d; |
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for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++); |
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if (i1 - prev1 > xenv->snake_cnt) |
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got_snake = 1; |
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kvdf[d] = i1; |
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if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) { |
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spl->i1 = i1; |
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spl->i2 = i2; |
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spl->min_lo = spl->min_hi = 1; |
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return ec; |
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} |
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} |
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/* |
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* We need to extent the diagonal "domain" by one. If the next |
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* values exits the box boundaries we need to change it in the |
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* opposite direction because (max - min) must be a power of two. |
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* Also we initialize the extenal K value to -1 so that we can |
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* avoid extra conditions check inside the core loop. |
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*/ |
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if (bmin > dmin) |
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kvdb[--bmin - 1] = XDL_LINE_MAX; |
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else |
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++bmin; |
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if (bmax < dmax) |
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kvdb[++bmax + 1] = XDL_LINE_MAX; |
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else |
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--bmax; |
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for (d = bmax; d >= bmin; d -= 2) { |
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if (kvdb[d - 1] < kvdb[d + 1]) |
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i1 = kvdb[d - 1]; |
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else |
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i1 = kvdb[d + 1] - 1; |
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prev1 = i1; |
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i2 = i1 - d; |
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for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--); |
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if (prev1 - i1 > xenv->snake_cnt) |
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got_snake = 1; |
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kvdb[d] = i1; |
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if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) { |
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spl->i1 = i1; |
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spl->i2 = i2; |
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spl->min_lo = spl->min_hi = 1; |
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return ec; |
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} |
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} |
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if (need_min) |
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continue; |
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/* |
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* If the edit cost is above the heuristic trigger and if |
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* we got a good snake, we sample current diagonals to see |
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* if some of the, have reached an "interesting" path. Our |
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* measure is a function of the distance from the diagonal |
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* corner (i1 + i2) penalized with the distance from the |
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* mid diagonal itself. If this value is above the current |
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* edit cost times a magic factor (XDL_K_HEUR) we consider |
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* it interesting. |
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*/ |
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if (got_snake && ec > xenv->heur_min) { |
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for (best = 0, d = fmax; d >= fmin; d -= 2) { |
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dd = d > fmid ? d - fmid: fmid - d; |
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i1 = kvdf[d]; |
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i2 = i1 - d; |
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v = (i1 - off1) + (i2 - off2) - dd; |
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if (v > XDL_K_HEUR * ec && v > best && |
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off1 + xenv->snake_cnt <= i1 && i1 < lim1 && |
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off2 + xenv->snake_cnt <= i2 && i2 < lim2) { |
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for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++) |
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if (k == xenv->snake_cnt) { |
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best = v; |
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spl->i1 = i1; |
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spl->i2 = i2; |
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break; |
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} |
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} |
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} |
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if (best > 0) { |
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spl->min_lo = 1; |
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spl->min_hi = 0; |
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return ec; |
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} |
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for (best = 0, d = bmax; d >= bmin; d -= 2) { |
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dd = d > bmid ? d - bmid: bmid - d; |
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i1 = kvdb[d]; |
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i2 = i1 - d; |
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v = (lim1 - i1) + (lim2 - i2) - dd; |
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if (v > XDL_K_HEUR * ec && v > best && |
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off1 < i1 && i1 <= lim1 - xenv->snake_cnt && |
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off2 < i2 && i2 <= lim2 - xenv->snake_cnt) { |
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for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++) |
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if (k == xenv->snake_cnt - 1) { |
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best = v; |
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spl->i1 = i1; |
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spl->i2 = i2; |
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break; |
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} |
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} |
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} |
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if (best > 0) { |
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spl->min_lo = 0; |
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spl->min_hi = 1; |
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return ec; |
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} |
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} |
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/* |
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* Enough is enough. We spent too much time here and now we collect |
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* the furthest reaching path using the (i1 + i2) measure. |
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*/ |
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if (ec >= xenv->mxcost) { |
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long fbest, fbest1, bbest, bbest1; |
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fbest = -1; |
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for (d = fmax; d >= fmin; d -= 2) { |
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i1 = XDL_MIN(kvdf[d], lim1); |
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i2 = i1 - d; |
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if (lim2 < i2) |
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i1 = lim2 + d, i2 = lim2; |
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if (fbest < i1 + i2) { |
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fbest = i1 + i2; |
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fbest1 = i1; |
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} |
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} |
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bbest = XDL_LINE_MAX; |
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for (d = bmax; d >= bmin; d -= 2) { |
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i1 = XDL_MAX(off1, kvdb[d]); |
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i2 = i1 - d; |
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if (i2 < off2) |
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i1 = off2 + d, i2 = off2; |
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if (i1 + i2 < bbest) { |
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bbest = i1 + i2; |
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bbest1 = i1; |
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} |
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} |
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if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) { |
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spl->i1 = fbest1; |
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spl->i2 = fbest - fbest1; |
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spl->min_lo = 1; |
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spl->min_hi = 0; |
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} else { |
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spl->i1 = bbest1; |
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spl->i2 = bbest - bbest1; |
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spl->min_lo = 0; |
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spl->min_hi = 1; |
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} |
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return ec; |
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} |
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} |
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return -1; |
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} |
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/* |
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* Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling |
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* the box splitting function. Note that the real job (marking changed lines) |
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* is done in the two boundary reaching checks. |
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*/ |
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int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1, |
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diffdata_t *dd2, long off2, long lim2, |
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long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) { |
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unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha; |
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/* |
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* Shrink the box by walking through each diagonal snake (SW and NE). |
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*/ |
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for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++); |
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for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--); |
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/* |
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* If one dimension is empty, then all records on the other one must |
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* be obviously changed. |
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*/ |
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if (off1 == lim1) { |
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char *rchg2 = dd2->rchg; |
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long *rindex2 = dd2->rindex; |
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for (; off2 < lim2; off2++) |
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rchg2[rindex2[off2]] = 1; |
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} else if (off2 == lim2) { |
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char *rchg1 = dd1->rchg; |
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long *rindex1 = dd1->rindex; |
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for (; off1 < lim1; off1++) |
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rchg1[rindex1[off1]] = 1; |
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} else { |
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long ec; |
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xdpsplit_t spl; |
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/* |
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* Divide ... |
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*/ |
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if ((ec = xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb, |
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need_min, &spl, xenv)) < 0) { |
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return -1; |
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} |
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/* |
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* ... et Impera. |
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*/ |
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if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2, |
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kvdf, kvdb, spl.min_lo, xenv) < 0 || |
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xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2, |
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kvdf, kvdb, spl.min_hi, xenv) < 0) { |
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return -1; |
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} |
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} |
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return 0; |
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} |
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int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, |
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xdfenv_t *xe) { |
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long ndiags; |
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long *kvd, *kvdf, *kvdb; |
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xdalgoenv_t xenv; |
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diffdata_t dd1, dd2; |
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if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) { |
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return -1; |
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} |
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/* |
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* Allocate and setup K vectors to be used by the differential algorithm. |
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* One is to store the forward path and one to store the backward path. |
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*/ |
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ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3; |
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if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) { |
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xdl_free_env(xe); |
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return -1; |
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} |
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kvdf = kvd; |
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kvdb = kvdf + ndiags; |
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kvdf += xe->xdf2.nreff + 1; |
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kvdb += xe->xdf2.nreff + 1; |
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/* |
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* Classical integer square root approximation using shifts. |
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*/ |
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xenv.mxcost = 1; |
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for (; ndiags; ndiags >>= 2) |
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xenv.mxcost <<= 1; |
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if (xenv.mxcost < XDL_MAX_COST_MIN) |
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xenv.mxcost = XDL_MAX_COST_MIN; |
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xenv.snake_cnt = XDL_SNAKE_CNT; |
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xenv.heur_min = XDL_HEUR_MIN_COST; |
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dd1.nrec = xe->xdf1.nreff; |
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dd1.ha = xe->xdf1.ha; |
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dd1.rchg = xe->xdf1.rchg; |
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dd1.rindex = xe->xdf1.rindex; |
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dd2.nrec = xe->xdf2.nreff; |
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dd2.ha = xe->xdf2.ha; |
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dd2.rchg = xe->xdf2.rchg; |
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dd2.rindex = xe->xdf2.rindex; |
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if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec, |
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kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) { |
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xdl_free(kvd); |
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xdl_free_env(xe); |
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return -1; |
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} |
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xdl_free(kvd); |
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return 0; |
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} |
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static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) { |
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xdchange_t *xch; |
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if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t)))) |
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return NULL; |
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xch->next = xscr; |
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xch->i1 = i1; |
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xch->i2 = i2; |
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xch->chg1 = chg1; |
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xch->chg2 = chg2; |
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return xch; |
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} |
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int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) { |
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xdchange_t *cscr = NULL, *xch; |
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char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg; |
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long i1, i2, l1, l2; |
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/* |
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* Trivial. Collects "groups" of changes and creates an edit script. |
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*/ |
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for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--) |
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if (rchg1[i1 - 1] || rchg2[i2 - 1]) { |
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for (l1 = i1; rchg1[i1 - 1]; i1--); |
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for (l2 = i2; rchg2[i2 - 1]; i2--); |
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if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) { |
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xdl_free_script(cscr); |
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return -1; |
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} |
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cscr = xch; |
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} |
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*xscr = cscr; |
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return 0; |
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} |
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void xdl_free_script(xdchange_t *xscr) { |
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xdchange_t *xch; |
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while ((xch = xscr) != NULL) { |
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xscr = xscr->next; |
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xdl_free(xch); |
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} |
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} |
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int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, |
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xdemitconf_t const *xecfg, xdemitcb_t *ecb) { |
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xdchange_t *xscr; |
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xdfenv_t xe; |
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if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) { |
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return -1; |
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} |
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if (xdl_build_script(&xe, &xscr) < 0) { |
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xdl_free_env(&xe); |
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return -1; |
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} |
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if (xscr) { |
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if (xdl_emit_diff(&xe, xscr, ecb, xecfg) < 0) { |
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xdl_free_script(xscr); |
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xdl_free_env(&xe); |
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return -1; |
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} |
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xdl_free_script(xscr); |
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} |
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xdl_free_env(&xe); |
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return 0; |
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} |
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